The present invention relates to a transceiver for use in a wavelength multiplex transmission method such as that described in German Patent No. 195 19 486 A.
British patent 2,308,461 A describes an optical transmitter having a reflective bandpass filter.
From the related art there are known transceivers having multiple inputs and outputs with glass fiber coupling for use in the wavelength multiplex transmission method. The wavelengths here are strictly separated, so there cannot be any interference in the transmitter and receiver. Influxes of wavelengths other than the intended wavelength causes interference in the transmitter, i.e., in the emitting laser source. Interference due to signals of a wavelength other than the desired wavelength on the receiving end leads to distortion of signals due to multiple signal groups being superimposed.
The transceiver according to the present invention, however, has the advantage that incoming and outgoing signals are separated by wavelength through at least one Michelson bandpass filter. Thus, both the receiver and transmitter are protected from signals of wavelengths which should not be received or transmitted by this transceiver.
A transceiver coupled into the wavelength multiplex network by an optical fiber is especially advantageous. Incoming and outgoing signals of different wavelengths are then separated through the bandpass filters in the transceiver and are sent either to the receiving photodiodes or output over the fiber in the case of the transmitter.
An advantageous embodiment has two separate optical fibers for input and output of the transceiver. This yields the advantage that the laser source can transmit on the same wavelength as the reception signal. The wavelength of the laser source need not differ from the reception wavelength as in the case of a fiber connection. An advantageous embodiment has a waveguide photodiode as the receiver, which can easily be integrated into a silicon chip, and where the received light can easily be input in the plane of the planar waveguide.
An advantageous embodiment of the transmission source is implemented with a semiconductor laser and a wavelength-selective Bragg grating which has been introduced into the planar glass waveguide structure on the silicon chip by UV light. This yields a very stable wavelength-selective source. It is also possible for the transmission source to be implemented by a glass waveguide laser.
The reflective bandpass filters are advantageously designed so that in a Mach-Zehnder interferometer structure (two series connected 3 dB couplers) the desired wavelength is reflected at the input at which the input signal is not connected through UV-induced Bragg gratings in the connecting arms of the input and output 3 dB couplers. With regard to the reflection characteristics of the UV-induced Bragg grating, this arrangement is a wavelength-selective Michelson interferometer. There is controlled processing, input or output, of transmission and reception signals. Interfering wavelengths due to wavelength crosstalk pass through cascaded bandpass filters without reflection and are drained off at the end.